This invention relates to the manufacture of metallic products having definite forms and made of steel or other metals, and more particularly to the forging of steel bars or steel wires into articles formed integrally with longitudinally arranged protuberances, such as camshafts.
In recent years, in place of the hot forging method, a cold forging method has become employed in working metal blanks into mechanical parts of various configuration, which can provide a final product in a simpler and more prompt manner merely be compressing a blank for the product placed in a die to be plastically deformed, with no substantial need for the deformed material to be cut.
According to the conventional cold forging method, a camshaft blank is first heated and the resulting heated blank is axially compressed at the opposite ends in a forging die having a predetermined mold configuration to form plane cams along the peripheral surface of the blank in a longitudinal arrangement.
However, the conventional cold forging method has the disadvantage that there occur discontinuities in the forged fibre flow at the roots of the plane cams thus formed, causing cracks in those roots, at worst. As a consequence, the resulting camshaft has very low mechanical strength and is not suitable for actual use.